This section introduces aspects that may facilitate better understanding of the present disclosure. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.
While the standardization of the fourth generation (4G) radio access technology (RAT), i.e. Long Term Evolution-Advanced (LTE-A), is still ongoing, the discussion on a Beyond 4G, which is usually referred to as 5G, system has already started. In the 5G system, requirements on latency are even tighter, which leads to a short round-trip time (RTT) with fast control signaling, and support for a flexible Uplink (UL)/Downlink (DL) ratio.
Accordingly, a physical subframe structure for 5G systems has been proposed, as illustrated in FIG. 1. As illustrated, each subframe or Transmission Time Interval (TTI) comprises a DL control region, an UL control region and a DL/UL data transmission region in this order. For example, the DL control region may be used by a base station to transmit a DL scheduling grant or an UL scheduling grant to a user equipment, or to transmit a HARQ feedback for an UL data transmission of the user equipment; the UL control region may be used by a user equipment to transmit a HARQ feedback for a DL data transmission; and the data transmission region may be used to transmit a DL data transmission from a base station or to transmit an UL data transmission from a user equipment, according to the respective scheduling grant. The control regions are located before the data transmission region so as to enable fast and cost efficient pipeline processing at a receiver.
Another proposal for a physical subframe structure for 5G systems is illustrated in FIG. 2. As illustrated, each subframe or TTI comprises a DL control region, a DL/UL data transmission region and an UL control region in this order. In this structure, the DL control region is located before the data transmission, which is located before the UL control region, so as to minimize HARQ RTT.
In LTE-A, Carrier Aggregation of multiple component carriers with subframes/TTIs of the same length being applied is adopted to improve throughput. However, in 5G systems, with carrier frequencies becoming further higher, subframes/TTIs of different lengths may be adopted on different carriers in even higher frequency bands.